1. The Field of the Invention
The present invention pertains to a method and apparatus for treating waste materials to recover the components thereof, and in particular to a method and apparatus which freezes the waste material, crushes it while in a frozen state, and separates the individual materials.
2. The Prior Art
The traditional method for handling waste materials has been to simply dump the waste on designated land areas thereby creating large and often hazardous dumps in which fires are frequent and runoff into water sources is routine. Not only are these dumps eyesores, they are environmental hazards to both the air and water. It is of no little consequence that while dumps or land fills have often been the cheapest short term way of handling waste material, the land which can be used for this purpose is rapidly running out. This is particularly true in the highly urbanized areas of the industrialized countries. This traditional method of disposing of waste does not allow for the recovery of materials thereby making some of these dumps and landfills potential mines of materials. This is a particular loss when materials, such as aluminum, are considered since many such materials can be recycled if they can be separated from other materials forming the original product.
A particular problem is found in the disposal of rubber based products, such as automotive tires, hoses and belts, all of which are comprised of natural or synthetic rubber reinforced with other materials such as metal belts and fiberous cords. These products have very little use after they have performed their original and/or primary task and therefor are generally discarded. It is acknowledged that a certain number of tires are used to build retaining walls, guards protecting boating and similar things where resistance to weathering is desirable. However, a far greater number of tires, belts and hoses are simply discarded to become eyesores and breeding grounds for insects and other pests. Burying is particularly ineffective with these materials since they resist decomposition and tend to work their way to the surface.
There have been many proposals for handling waste materials so as to recover the component products. Some of these included burning off the unwanted material to get at the fire resistant residues or metal substructure. While this may seem to be an answer, it ignores the fact that much useful material would be consumed in burning, that the incineration process itself would not be energy efficient and could release hazardous byproducts into the atmosphere. This also ignores the problem of what to do with the ash residues.
Other approaches to material recovery have included rendering the waste material into smaller pieces and then forcably removing the desirable components. This may be a very difficult task when one considers recovery of materials from something such as a tire, which is produced to withstand much abuse without loss of function. Even rendering a tire into smaller pieces would still not enhance the recovery of the metal, fiber, and rubber products thereof. Besides, a great amount of energy would be consumed in rendering the tire into the smaller pieces.
Still other approaches have involved the use of chemicals to break down the materials into their components. However, these methods create chemical sludges and residues which are not only a nuisance (if not impossible) to dispose of, but some chemical treatments are dangerous to both human life and the environment.
There have been a number of attempts to improve on the above discussed techniques by freezing and treating waste material. U.S. Pat. No. 2,609,150 teaches precooling thermal plastic resins and then driving the material at high velocity to shatter upon impact with a barrier. U.S. Pat. No. 3,718,284 relates specifically to automobile tires and includes a pretreating step which punctures holes in the tire in order to assure drainage of the liquid refrigerant. The puncturing step would demand a large energy expenditure. U.S. Pat. No. 2,836,368 relates to treating food products which have a large liquid content of their own. The product is frozen by a stream of gas and the frozen material is pulverized. U.S. Pat. No. 3,885,744 describes an apparatus which sequentially freezes, crushes, and separates material. The separating steps are specified as including magnetic means. U.S. Pat. No. 3,995,816 also relates to automobile tires. According to this patent, the tires are frozen and dropped onto a rotor to be crushed sufficiently to pass on through the apparatus. U.S. Pat. No. 4,025,990 differs from the previously discussed patents in that it discloses having at least two separate freezing zones. U.S. Pat. No. 4,073,443 discloses an apparatus which clearly is batch operated rather than continuously operated. U.S. Pat. No. 4,084,387 discloses an apparatus in which a helix within a drum is utilized to move the product forward.
The present invention intends to overcome all of the above difficulties.